Description: Benzoic acid is a flake or needle-like crystal, with benzene or formaldehyde odor, flammable. Relative density 1.2659. Melting point 122.4 ℃, boiling point 249 ℃, refractive index 1.504. Vapor volatile. Flash Point (closed cup) 121-123 ℃. Slightly soluble in water, soluble in ethanol, methanol, ether, chloroform, benzene, toluene, carbon, carbon tetrachloride and turpentine.
In 100 ℃ rapid sublimation, can be accompanied by water vapor volatilization. Benzoic acid is commonly found in the natural world in the form of free acids, esters, or derivatives. For example, in the Benzoin gum in the form of free acid and benzyl ester, in some plants in the leaves and stems of the skin in the form of free, in the flavor of methyl ester or benzyl ester, in the horse urine in the form of its derivative of equine uric acid.
Production method: The first by the benzoin gum distillation or alkali water hydrolysis system, can also be hydrolyzed by the horse uric acid. The industrial production method of benzoic acid has three kinds of toluene liquid phase air oxidation method, Zaki three chlorine water solution and phthalic anhydride Denitration method, and the toluene liquid phase air oxidation method is most common. Toluene and air into the reactor containing cobalt naphthenate catalyst, in the reaction temperature 140-160 ℃, operating pressure 0.2-0.3mpa under the conditions of the reaction, the formation of benzoic acid, steamed to the reaction of toluene benzoic acid, and then through decompression distillation, Recrystallization finished. The final product is not easy to refine with phthalic anhydride, and the production cost is high, which is only used in the manufacture of products with small quantities of medicine.